Truck-mounted paper shredding assemblies ("shredders") are commonly in use today. These units move about from one office to another to shred often confidential paper documents.
Most of the prior art shredders of this type use knives or cam type cutting devices to shred the paper into strips. In general, these shredders rely on manual feeding of paper to ensure that the paper enters the machine at an even thickness and rate. As a consequence, they are relatively slow in processing paper.
U.S. Pat. No. 5,542,617, issued to D. E. Rajewski, discloses a different and faster type of shredder--it utilizes a rotary hammer mill to shred the paper. More particularly this shredder comprises:
A circular feed tub, into which the paper to be shredded is dumped. The tub floor forms a slot or opening; PA1 The hammer mill is positioned beneath the opening. The rotating hammers of the mill protrude through the opening, when the mill is operating, and pull in paper--this paper is shredded as the hammers pass through close-fitting gaps formed between spaced apart steel fingers; PA1 A rotating sweep arm is positioned in the tub . The arm is spaced above the tub floor, to avoid contact with the hammers. It functions to bias paper in the tub to the hammer mill opening; PA1 The mill includes a trough-like curved screen cupping its bottom half. The paper is further shredded as the hammers force it through the screen; PA1 The shredded paper drops into an open-top trough positioned beneath the mill. The trough changes into a tubular chute at its far end, which chute extends into a closed box forming a storage chamber. A plunger reciprocates lengthwise in the trough to push the paper through the chute into the storage chamber and, in doing so, to compress paper already in the chamber; PA1 The box forming the storage chamber has a movable side wall which can be advanced by a cylinder to empty the box by driving its contents through an opposed, hinged box side wall into a waiting receptacle such as the box of a second truck. PA1 The sweep arm rotating over the protruding hammer ends is spaced above the tub floor. As a result, paper is left on the floor after completion of the shredding operation. This is undesirable when shredding confidential documents; PA1 The paper is fed at an angle into the hammers by the rotating sweep arm. This leads to deflection and bending of the hammers, which has proved to be a significant maintenance problem; PA1 Fine particles ("dust") generated by the shredding process create various problems. For example, the reciprocating plunger, biasing shredded paper through the bottom trough and chute, creates a back flow of air from the storage area on each stroke. This back flow carries dust with it back into the loading and shredding zones. As a result the machine must be cleaned frequently and maintenance costs are affected. In addition, heat produced by the moving parts can ignite the dust and has caused fires. PA1 Furthermore, the dust can leak from the machine, which makes it unpleasant to work with; and finally PA1 The storage box is a permanent part of the unit, requiring the continuing presence of a second truck for receiving the load of shredded paper once the storage box is loaded.
There are a number of problems associated with the '617 shredder. More particularly:
The present invention is directed toward improving the '617 shredder design, to solve these problems.